AIM Protective effects of scutellarin (SCU) on myocardial ischemia reperfusion (I-R) in rats was evaluated, different SCU treatments were compared and SCUs effect-time relationship was also investigated in the present study.METHODS Myocardial I-R injury model was established by ligation of left anterior descending branch of coronary artery in rats for 40 min, and then carrying on reperfusion for 120 min.The left ventricle was isolated and cut into slices, the slices were stained with TTC, observe the change of the ischemic area, and evaluate the protective effect of SCU on myocardial I-R injury in rats.RESULTS ① Intravenous infusion of SCU can reduce the ischemic area percentage in myocardial I-R rats.SCU (45, 90, 180 mg· kg-1) significantly reduced ischemic area.SCU can decrease the activity of LDH in plasma in myocardial I-R rats.Compared with model group, SCU (90, 180 mg·kg-1)significantly decreased the activity of LDH in plasma in myocardial I-R rats.② SCU pre-treatment, post-treatment and treatment during I-R showed protection in myocardium I-R rats.The effect is most potent when rats were treated with SCU during I-R, compared with model group, SCU 180 mg·kg-1 significantly reduced ischemic area.③ During 0-120 min after SCU treatment, protective effect of SCU on myocardial I-R injury in rats wore off with time prolongation.0, 30, 60 min after SCU 180 mg·kg-1 treatment, SCU significantly reduced ischemic area.120 min after SCU treatment, the effect was not significant.CONCLUSION SCU treatment attenuated injury in myocardial I-R rats.SCU pre-treatment, post-treatment and treatment during I-R had preventative and therapeutic effects in myocardial I-R rats.